<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .left {
            width: 200px;
            height: 300px;
            background-color: red;
            /* float: left; */
            /* position: absolute;
            left: 0; */
        }

        .right {
            width: 200px;
            height: 300px;
            background-color: blue;
            /* float: right; */
            /* position: absolute;
            right: 0; */

        }

        .center {
            flex: 1;
            height: 300px;
            background-color: green;
            /* margin: 0 200px; */
        }

        /* .a {
            width: 100%;
            height: 100px;
            background-color: black;
        } */
        .father {
            display: flex;
        }
    </style>
</head>

<body>
    <div class="father">
        <div class="left"></div>
        <div class="center"></div>
        <div class="right"></div>
    </div>
    <!-- <div class="a"></div> -->
</body>

</html>